The development of alpha olefin oligomerization techniques for the production of linear alpha olefins (C6 to C20) which do not utilize triethylaluminum (TEA) as part of the catalyst system has been a challenge. Both the economics and relative efficiency of TEA-based techniques have been difficult to match in alternative techniques. Some commercial success has been achieved using alternative techniques which use homogeneous catalyst systems; these techniques generally require extended secondary processing to recover the linear alpha olefins from undesired fractions/products such as butene or waxes.
Commercial selective olefins technology, based on pyrrole and PNP ligated chromium complexes, produce 1-hexene and/or 1-octene, without the generation of other undesirable fractions such as butene or waxes. The reaction mechanism operates via a unique metallocycle mechanism, with catalyst systems generated via treating a chromium compound/complex with an activator. These activators are typically based on materials such as aluminum alkyls, alkylaluminoxanes, borates, etc. Activation can be done in batch methodology prior to introducing the catalyst system to a reaction zone, or in a continuous method in which the components are mixed in a reaction zone, and then continuously added to a second reaction zone containing ethylene.
Improper activation can lead to a variety of undesired effects including, without limitation, the co-generation of by-products, such as cyclopentane(s), mixed C10's, C12's, and C14's, and polyethylene. The co-generation of polyethylene polymer can lead to reactor wall fouling that can cause reduced run time, loss of heat transfer for cooling the exothermic reaction, and poor overall reactor performance. Accordingly, there is an ongoing need for improved activators that provide for complete activation of chromium compounds while reducing the co-generation of undesired by-products.